1. Field of the Invention
The invention relates to a voltage supply circuit for provision of an internal supply voltage in an integrated circuit. The invention also relates to an integrated dynamic random access memory (DRAM) circuit having a voltage supply circuit. In addition, the invention relates to a method for controlling a supply source, in particular for an integrated circuit.
2. Description of the Related Art
Internal supply sources which apply defined supply potentials to internal supply lines are provided for operation of integrated circuits, in particular semiconductor memory modules. The supply sources are normally operated actively both during normal operation and when the integrated circuit is in a standby mode, in order to make it possible to provide the supply currents which are required in the respective operating mode to the internal supply lines.
Particularly for mobile applications, it is desirable to reduce the current drawn by an integrated circuit, in particular the current drawn in the standby mode. This is generally achieved by a reduction of leakage currents and by improved circuit design.
The supply current during the standby mode depends on a large number of factors, which make it difficult to determine the magnitude of the supply current in advance. By way of example, the supply currents in the standby mode for an integrated DRAM memory circuit are governed by the refreshing of the contents of the memory cells, the leakage currents and the analog components which are activated in the standby mode.
Supply sources for generating an internal supply voltage, in particular for the standby mode of integrated circuits, are thus designed such that they can supply the necessary supply current in any operating mode. The efficiency of such supply sources is accordingly governed by the maximum supply current which they can provide on the internal supply line and the overall current draw which the supply source has for this purpose. A voltage supply circuit which is designed to provide a supply current for normal operation generally has poorer efficiency when providing a smaller standby current since a constant operating current, which is essentially independent of the supply current, is required for operation of the supply source when there is no load current on the internal supply line. Such a voltage supply circuit is thus generally overdesigned in the standby mode. As a result, the current draw of the integrated circuit in the standby mode is greater than it need be for optimum matching of the supply source to the current that is required in the standby mode.